1. Field of the Invention
The present invention relates to a shock detecting device, and more particularly to a shock detecting device which mechanically ignites an ignition element without electric power for use as a starting sensor of an anti-shock safety system such as an air-bag and a seatbelt tensioner.
2. Description of the Prior Art
A conventional shock detecting device is disclosed, for example, in Japanese utility model application laid-open publication No. 2(1990)-115056. In this prior shock detecting device, when a shock which is more than a predetermined value is applied from outside, a weight is moved by the shock and then one end of a release lever is pressed by the movement of the weight. Then, the release lever is rotated and the engagement between the other end of the release lever and a firing pin is released. Thereby, the firing pin is projected to the outside of a housing by an urging force of a spring and an ignition element such as a primer is struck by the firing pin.
The above conventional shock detecting device includes a safety mechanism which prevents the operation of the shock detecting device due to the shock in order to prevent an erroneous operation of the shock detecting mechanism before an installation to an anti-shock safety system. The safety mechanism is comprised of a spring urged rock lever which is rotatably supported on the housing and which is engaged with the weight through the release lever and which is positioned on a locus of the movement of the weight and a rock shaft which is movably supported on the housing and which makes the rock lever rotate against the urging force of a spring by means of a cam. Thereby, the safety operation condition under which the weight is not moved by the applied shock is obtained by the engagement between the rock lever and the weight through the release lever. In this safety operation condition, when the rock shaft is moved and then the rock lever is rotated toward the outside of the locus of the movement of the weight against the urging force of the spring by the movement of the rock shaft, the engagement between the rock lever and the weight through the release lever is released. Thereby, the safety release condition in which the weight can move by the applied shock is obtained.
In the safety mechanism of the above conventional shock detecting device, however, the rock lever has to be engaged with the weight through the release lever in order to prevent an easy changeover from the safety operation condition to the safety release condition, namely in order to prevent the rotation of the rock lever due to the movement of the weight according to the shock which is more than the urging force acting on the rock lever. Thereby, extreme accuracy is required to the form and the arrangement of the release lever in order to improve the reliability of the safety device which has to reliably prevent the movement of the weight. Therefore, the manufacturing cost of the shock detecting device is increased and the assembling performance is deteriorated.